This may or may not be interesting to some or all. I was cleaning out some old storage areas in my garage, and came across an item that really bridges a wide expanse of computing as we know it. The ‘geezer’ is me. Well before subsecond response times, nanoelectronics, the ‘chip’, certainly microprocessors, LED’s, and the like were some pretty crude looking parts. The picture you are looking at, I took with my ‘digital’ camera (no longer film) this afternoon out on the picnic bench. You need to be logged in to see the picture.
You are looking at ‘core memory’. The black toroidal cores in the picture are 1 (one) bit each. You could put several hundred of these in a tablespoon. 8 bits to a byte. You should see 10X10 matrices. The copper colored wires are the address lines X and Y, and you should notice a second copper wire running in parallel with one of the address lines. The second copper wire is the ‘Read line’. Notice next the green line, that’s the inhibit line. This memory ran at about 60 volts. Each time the memory was addressed, the ferrite core would want to flip to the opposite state. If it was a 0 it would switch to a 1, unless an “inhibit line” was active at the same time that the addressing and read lines were. This would cancel out the magnetic field generated, and leave it’s state as it was.
That’s the ‘so what’ part. The interesting part of this technology was that this type of memory lasted until the bipolar transistor replaced it. Even more interesting is that these core storage units were actually a cottage industry. These were built by women in upstate New York. Those wires are actually hand sewn. Yep! A 64KiloByte storage unit cost about $100,000 to be built and tested. So when we think about ‘concise’ programming techniques, major applications in geezer times were of course single threaded applications (like our Arduino’s) and very memory constrained. Just thought I’d share this with the group.